Heat Exchanger and Method For Cooling Network Cabinets

ABSTRACT

The invention relates to a heat exchanger for water-cooled network cabinets and to a method for cooling network cabinets, particularly server cabinets. The heat exchanger is constructed as an air-water heat exchanger in redundant form and ensures a leaktight arrangement and cooling in a network cabinet. The heat exchanger has two heat exchanger elements with separate cooling water connections which, accompanied by the formation of a space, are provided for the supply of exhaust air from the cabinet interior. A partition is adjustably placed in the space and in the case of a fault, e.g. if one heat exchanger element or a cooling circuit fails, the corresponding heat exchanger element is aerodynamically blocked with the aid of the partition. The entire exhaust air is cooled in the intact heat exchanger element and supplied to the cabinet interior, so that no interruption of operation is necessary.

The invention relates to a heat exchanger for liquid-cooled networkcabinets according to the preamble of claim 1 and to a method forcooling network cabinets according to the preamble of claim 19.

Known heat exchangers for liquid-cooled network cabinets are air-liquidheat exchangers, particularly air-water heat exchangers, which aresuitable for removing high power losses from the network cabinet,particularly server cabinets.

In DE 20 2004 006 552 U1 and WO 2005/104 642 A1 and the “CoolTherm”internet entry of KNÜRR AG a liquid-cooled sewer cabinet is known, whichhas in the lower area and therefore below the superimposed servers anair-water heat exchanger. The heat exchanger is connected to the coldwater supply of the building, the initial water temperature isapproximately 12° C. and the total waste heat is eliminated to theoutside via the cooling water circuit without impairing the airconditioning. The air in the cabinet flows in a closed circuit andadvantageously there are equally long flow paths through all theservers. The cooling air is frontally sucked out of the heat exchangerby the server fans at a temperature of 20 to 25° C. and is removed atthe back with an increased temperature. This exhaust air is sucked inbehind the servers and is forced with the aid of fans through an exhaustair duct in the rear door of the cabinet downwards into the heatexchanger.

The known CoolTherm server cabinet with the air-water heat exchangerlocated at the bottom ensures high cooling capacities above 4 to 6 kWper cabinet, so that high power servers can be installed and servercabinets with a very high packing density can be set up, also ininterlinked manner, in computing centres and the like.

There is an increasing need in the case of server cabinets for highavailability or fault tolerant computing centres to redundantly designall the functionally critical components.

In the case of the CoolTherm server cabinet fans are e.g. provided witha n+1 redundancy. The air-water heat exchanger as a purely passivecomponent admittedly has a relatively limited probability of failure.However, there is no 100% fail safety.

The Liquid Cooling Package (LCP) of RITTAL (cf. RITTAL internet entry,product catalogue HB31/System Air Conditioning) permits the formation ofredundancies on the heat exchanger side. The LCP comprises a coolingrack, which is laterally located on a server cabinet or also between twoserver cabinets and can receive up to three or even four air-water heatexchanger cooling modules, which are superimposed. When there are twoserver cabinets with a LCP between them and in each case one lateralLCP, the central LCP constitutes the redundancy for the in each caseright and left-hand server cabinet.

As a result of the lateral arrangement of the heat exchanger modules orthe cooling rack, said cooling system has a greater leak risk and alsoleads to greater space requirements and due to the greater width doesnot satisfy the reference grid of cabinet rows in computing centers.

The object of the invention is to develop an air-liquid heat exchanger,which is redundantly constructed and also ensures a compactassembly-friendly and maintenance-friendly, as well as leaktightarrangement in a network cabinet, particularly in a server cabinet. Atthe same time the redundant heat exchanger must be compatible with theefficient air-liquid heat exchangers hitherto used in the CoolThermserver cabinet. Through a method for cooling network cabinets,particularly server cabinets, with the aid of a redundantly constructedair-water heat exchanger it must be possible to ensure the full coolingcapacity without any interruption of operation in the case of a fault.

From the apparatus standpoint the object is achieved according to theinvention through the features of claim 1. From the method standpointthe object according to the invention is achieved through the featuresof claim 19. Appropriate and advantageous developments appear in thesubclaims and the specific description relative to the drawings.

A fundamental idea of the invention is to achieve compatibility andredundancy through an appropriate arrangement of two heat exchangerelements in a heat exchanger housing and to provide the two independentheat exchanger elements with separate cooling water connections. It isadvantageous if the two heat exchanger elements, which can e.g. beconstructed as mutually independent tubular/finned blocks, can in eachcase be detachably connected to the forward and return run of separatelines of a cold water network or main or a recooler.

According to the invention a partition is adjustably placed in an airintake-side open space of the heat exchanger formed by the heatexchanger elements arranged at an angle to one another. This partitioncan be pivoted from a position in which both heat exchanger elements aresubject to the action of the exhaust air to be cooled and which ispreferably a central position, into a blockade position. The blockadeposition leads to a covering of in each case one of the two heatexchanger elements and therefore to an aerodynamic blocking of theexhaust air supply with the consequence that in each case the other heatexchanger element is subject to the action of the entire exhaust airflow.

From the method standpoint, in normal operation the two heat exchangerelements are subject to the action of a cooling liquid, preferably coldwater from the building mains or cooling water from a special coolingwater network or main of the computing center and also the exhaust airsubject to the dissipated heat. In normal operation the adjustablepartition is in the central position and the exhaust air flow enteringthe heat exchanger via an air intake side is distributed over both heatexchanger elements. The air flowing through both heat exchanger elementspasses out as cooling air from said two heat exchanger elements into anair exit area and is supplied to the servers and/or similar componentsto be cooled.

In the case of a fault the partition is brought into the blockadeposition. A fault can be the failure of a heat exchanger element, e.g.due to a leak or a stoppage. Another fault case is constituted by afailure of a cooling circuit, when the connected heat exchanger elementcan no longer be supplied with cooling water. If a cooling circuit failsthen through a temporary pivoting of the air conduction flap the entireexhaust air flow can be passed through the heat exchanger elementconnected to the intact cooling circuit. Thus, the server cabinet cancontinue to be operated until the fault is removed. It is merelynecessary to pivot the air conduction flap in such a way that anaerodynamic blocking of the exhaust air supply to the heat exchangerelement with the failed cold water supply is ensured. The prerequisiteis an independent cooling water supply of the two heat exchangerelements, which is particularly advantageous in high availabilitycomputing centers.

In a preferred embodiment the two heat exchanger elements have aparallelepipedic construction and are so positioned that the airintake-side space is V-shaped in horizontal section and the air exitarea is roughly W-shaped. Generally the air intake side of the heatexchanger housing of an inventive heat exchanger placed in a servercabinet e.g. at the bottom, is located on the rear of the cabinet and anair exit side of the heat exchanger housing is located in the frontcabinet area. Thus, air flows in the front direction through the heatexchanger from the cabinet rear. However, a turned-around arrangement oran arrangement modified by 90°, including the cabinet side walls, isalso possible.

Appropriately the adjustable partition located in the air intake-sidespace is vertical and is dimensioned corresponding to the verticallongitudinal side of the identically constructed heat exchanger units,which bound the roughly V-shaped space and if necessary are to becovered by the partition, so that the necessary “unilateral” blockadefor the exhaust air flow is ensured.

It is advantageous that the partition can be adjusted about a verticalpivoting axis, which in the space is located close to the air exit area.Appropriately the pivoting axis is located in the zone of the virtuallyadjacent, vertical inner edges of the two heat exchanger elements.

If the two heat exchanger elements are in each case placed on aseparate, horizontally adjustable support element, each support elementwith the relevant heat exchanger element and independently of the othersupport element can be extracted from the heat exchanger housing. In thecase of a fault due to a defect to one of the heat exchanger elements,e.g. when a leak or stoppage occurs, the defective heat exchangerelement can be extracted from the heat exchanger housing afterseparation from the cooling water system, then dismantled and repairedor replaced by a new element. There is no need to interrupt operationfor this and the removal of the dissipated heat from the exhaust airflow takes place entirely in the second, operable heat exchanger elementas soon as the defective heat exchanger element is covered following apivoting movement of the partition.

Appropriately the lower part of the heat exchanger housing is formed bya condensate/leakage water collecting tank, which is constructedcontinuously and can be connected to a condensate drain pipe. Thus, aleakage risk is reduced to a minimum or is virtually excluded.

It is advantageous if the partition can be fixed in the central positionimplementing the normal position and optionally also in the two possibleblockade positions. This ensures that there can be no change to thepartition position in an unintentional manner.

After releasing the fastening or a locking action, the partition can beadjusted from the central position by hand or with the aid of a drive,e.g. a gas pressure spring or an electric motor and brought into theblocking position. In the same way the return to the central positioncan be brought about when the fault is removed and normal operation canagain be carried out with action on both heat exchanger elements.

Appropriately in the vicinity of the two heat exchanger elements andtheir cooling water supplies there are sensors for fault detection andfor emitting fault or warning signals, particularly flow and leaksensors. The pivoting of the partition for blocking the in each case nolonger operable heat exchanger element takes place manually or by meansof a drive following the warning signal. There can also be an automaticpartition adjustment.

If the movable partition is pivoted against one of the heat exchangerelements and prevents the air flow through said element, so that theentire airflow is guided through the other heat exchanger element, theservers, switches and the like installed in a cabinet are supplied withcooling air from the flowed-through heat exchanger element. To ensure auniform server cooling air supply, air conducting elements, which arepreferably adjustable and can be in the form of flaps, are located inthe air exit area and/or in the cabinet area following the air exit fromthe heat exchanger housing. The unilaterally exiting cooling air flowcan be directed and “spread out” over the entire cabinet width by theair conducting elements in order to ensure the uniform cooling airsupply for the servers, etc.

In order to ensure the full cooling capacity in the case of a fault withone operable heat exchanger element, it can be appropriate to operatethe fans for the exhaust air flow at a higher speed. The cooling airflow can then be maintained even against an increased flow resistance.It is also possible to specify one server cabinet or network cabinetwith a redundant heat exchanger with a lower nominal cooling capacity.The servers and similar components installed in the cabinet can thencontinue to operate uninterruptedly with an adequate cooling capacityuntil the fault is removed. Operation does not have to be interrupted.

This also applies when replacing a heat exchanger element with extractedsupport element and an opened cabinet door. The installed servers andthe like then suck the ambient air from the installation area, which isnot exposed to heated exhaust air. The server exhaust air subject to thedissipated power is deheated in the second, operable heat exchangerelement, i.e. cooled back and blown in heat-neutral manner into theambient air. It is advantageous that the service technician can workoutside the cooling air flow, because the air supply to the defectiveheat exchanger element is interrupted with the aid of the partitionpivotable into the blockade position.

The adjustable partition can be extended over and beyond its verticalpivoting axis in the direction of the air exit side and can extend up toa covering of the air exit side or up to the front door of the cabinet.At least in the air exit area the extended partition is positioned infixed manner and together with the pivotable partition subdivides theheat exchanger into two virtually identically sized areas.

In a further development of the heat exchanger and a network cabinet,particularly a server cabinet, in which the inventive redundant heatexchanger is located, on the air exit side the heat exchanger housing isseparately covered by two coverings, which are associated with the givenheat exchanger element and can e.g. be constructed in flap or door-likemanner. The cabinet door can then be shortened. For example the loweredge of the cabinet door can extend close to the upper covering of theheat exchanger housing. In this construction it is advantageous that thecabinet door does not have to be opened if a heat exchanger element hasto be extracted for removing a fault. There is no air suction from theinstallation area of the cabinets.

It is appropriate if on the air exit side each heat exchanger element isprovidable with an arresting element which, when the heat exchangerelement is extracted, prevents ambient air from entering the supply airduct of the cabinet and the server housing. The arresting element can beconstructed as an additional flap or also as a horizontally adjustableor displaceable plate and is e.g. arranged or guided on the heatexchanger housing. The two arresting elements associated with the heatexchanger elements are appropriately operable independently of oneanother.

On replacing a heat exchanger element initially the particular coveringor flap or door is opened in order to be able to extract the supportelement with the heat exchanger element, whilst the covering of thesecond, operable heat exchanger element remains closed. The entirecooling air flow from said second heat exchanger element can then,appropriately with the arresting element in the arrested position and bymeans of guiding elements, can be directed upwards into the suction areaof the servers. After replacing the defective heat exchanger element theair exit side covering is closed again, the arresting position of thearresting element is cancelled out and the adjustable partition ispivoted back from its blockade position into the central position foreffecting normal operation.

The space between the air exit side of the heat exchanger housing andthe front door of the server cabinet can contain a guiding device fordeflecting the cooling air flow. Such a guiding device can be basicallyconstructed as described in DE 20 2004 016 492 U1 and as shown inexemplified manner in FIGS. 3 to 5 thereof. Corresponding to the twoheat exchanger units and a unilateral cooling air flow in the case of afault it is appropriate to construct the air guiding device in one ortwo parts and then a vertical separating element is located in thecenter and is aligned with the fixed partition. The fixed partition partcan, in an alternative construction, also be an integral part of saidair guiding device. The guiding device can be located on the heatexchanger housing or on the inside of the cabinet front door. Whenpositioning on the heat exchanger housing the air guiding device shouldbe fixed in detachable manner, so as to ensure the extraction of theheat exchanger elements.

The connection of the heat exchanger elements to a cold water network ormain of the building, a specific cold water main of the computing centeror a recooler for a cooling liquid can, as desired, take place on theair intake or air outlet side. If the detachable connections are broughtabout by quick couplers, the connection can be automatically released indrip-free, sealing manner on extracting a heat exchanger element and canbe restored on inserting the heat exchanger element.

The inventive, redundant heat exchanger is not restricted to use innetwork cabinets and server cabinets and can instead be used for allcooling concepts and cooling arrangements. The advantages are a completeredundancy accompanied by a relatively limited constructional andmanufacturing expenditure. A network cabinet, particularly a servercabinet, which is equipped with the inventive heat exchanger can, in thecase of a fault in the area of one of the two heat exchanger elements orin the cooling water main, can continue to be operated. A defective heatexchanger element can also be replaced without interrupting operationand without either problems or particular urgency.

The invention is described in greater detail hereinafter relative to theattached diagrammatic drawings, wherein show:

FIG. 1 A perspective view of an inventive, redundant heat exchanger witha partition in the central position for normal operation and with an inpart removed housing.

FIG. 2 A heat exchanger according to FIG. 1, but with a partition in theblockade position provided for a fault.

FIG. 3 A network cabinet with an inventive, redundant heat exchanger andwith a partition in the blockade position and an extracted heatexchanger element.

The heat exchanger 2 of FIGS. 1 to 3 has a housing 6, which for a clearreproduction is broken away in the area of an upper covering 26 and aside wall 28. Two heat exchanger elements 3, 4 are positioned at anangle to one another in the housing 6, so as to form a V-shaped space 5between the heat exchanger elements 3, 4. The identically constructedheat exchanger elements 3, 4 are arranged in virtually adjacent mannerwith vertical inner edges 15 in the vicinity of an air exit side 8 ofthe heat exchanger housing 6, so that exhaust air, which enters thespace 5 on the opposite air intake side 7 of the heat exchanger 2, isguided through the two heat exchanger elements 3, 4 arranged in an edgemanner.

In the space 5 is provided a partition 10, which can be pivoted to theright and left about a vertical pivoting axis 11 until engagement takesplace on the given vertical, inside longitudinal side 19 of the heatexchanger elements 3, 4.

For normal operation the partition 10 in FIG. 1 is located in a centralposition. The exhaust air entering at an open air intake side 7 (blackarrow) is subdivided by the partition 10 and passes into both heatexchanger elements 3, 4, is cooled and then passes in the form ofcooling air into an air exit area 9 and via the air exit side 8 of theheat exchanger 2 into a not shown, supply air duct and is sucked in bythe server fans, which are in each case located in a housing.

The partition 10 is vertically oriented and dimensioned for covering thevertical longitudinal sides 19 of the heat exchanger elements 3, 4 ineach case bounding the space 5. In this embodiment the heat exchangerelements 3, 4 are parallelepipedic and engage with their narrowlongitudinal sides on the bottom support elements 16, 17.

On the air intake side 7 are provided detachable connections 13, 14 fora separate connection of the heat exchanger elements 3, 4 to thebuilding cold water main or to a recooler. The connections 13, 14 forthe forward and return passage of a cooling agent, e.g. cold water fromthe building cold water main, are advantageously constructed as quickcouplers.

In this embodiment the separate support elements 16, 17 are supportplates, which are virtually adjacent to one another and which can beforwardly separately extracted (cf. FIG. 3). The partition 10 shown inFIG. 1, as a result of the symmetrically arranged heat exchangerelements 3, 4, also constitutes the separation line of support elements16, 17. Below the support elements 16, 17 is provided acondensate/leakage water receiving tank 18, which can be connected to anot shown condensate drain pipe.

FIG. 2 shows the heat exchanger 2 in the case of a fault. When a faultoccurs in one of the two connected cooling water circuits 13, 14 or inone of the heat exchanger elements 3, 4, which leads to an interruptionof the cooling water supply, the partition 10 is pivoted against thefailed heat exchanger element, which in FIG. 2 is the left-hand element4. The pivoting of partition 10, which can take place manually,mechanically or automatically (not shown), takes place up to theblockade position, in which the air flow is completely diverted to theheat exchanger element 3. In the embodiment of FIG. 2 the partition 10engages on the heat exchanger element 4 and covers the air intake side19. The exhaust air flowing into the space 5 is now exclusively guidedthrough the operable heat exchanger element 3 and the exiting coolingair passes via the air outlet area 9 and the air outlet side 8 of theheat exchanger 2, e.g. via a supply air duct 21 (FIG. 3), to the serversof a server cabinet.

In the operating state of the redundant heat exchanger 2 shown in FIG. 2said servers are supplied solely with cooling air from the single heatexchanger element 3. There is no need to interrupt operation foreliminating a defect or for carrying out a repair due to the redundantconstruction of the heat exchanger 2.

FIG. 3 shows a server cabinet 20 equipped with the inventive, redundantheat exchanger 2, which is positioned at the bottom and below an innerarea 25. With respect to said server cabinet 20, whose right-hand, frontcorner region is broken away to facilitate understanding, are shownparts of the basic frame 29, an upper covering 30 with cable bushing 31and vertical installation beams 24, which are inter alia used for theinstallation of the not shown servers. At the front there is a supplyair duct 21 for the cooling air (light arrows) from the heat exchanger 2and at the rear an exhaust air duct 22 with fans, whereof it is onlypossible to see the openings 23 in a wall 27 of the exhaust air duct 22.

The defective heat exchanger element 4 together with the associatedsupport element 7 is frontally extracted from the heat exchanger 2 andtherefore from the server cabinet 20 and can in this position bereplaced or repaired.

If the front cabinet door extends over the entire height of the cabinet20 (not shown), opening thereof is necessary. The servers (not shown)stacked in the inner area 25 of the cabinet 20, during this time aresupplied with ambient air which, as a result of the cooling air guidedin closed circuit form, is suitable for cooling in the individualcabinets. The entire exhaust air is cooled in the heat exchanger element3 and passes as cooling air via the frontally opened cabinet into theroom or environment.

The inventive heat exchanger 2 of FIGS. 1 to 3 is provided in the airexit area 9 with a fixed partition 12, which can be constructed as anextension of the pivotable partition 5. Said fixed partition 12 in thisembodiment projects over and beyond the air exit side 8 of the heatexchanger 2 and extends virtually up to the not shown, front door of thecabinet 20 in FIG. 3.

In broken line form in FIG. 3 is shown an alternatively constructedcabinet, which has a shortened front door 33 and a covering 35 on theheat exchanger 2, as well as an arresting element 37.

The shortened front door 33 of the cabinet 20 extends up to the heatexchanger housing 6 or to the upper covering 26 and the horizontallyoriented arresting element 37 in the arresting position. The arrestingelement 37 is associated with the left-hand heat exchanger element 4which, when the covering 35 is opened is extracted together with supportelement 17 from the cabinet in order to eliminate a defect. The aircooled in the right-hand heat exchanger element 3, as a result of thefixed partition 12 and a not shown covering of the right-hand heatexchanger element 3 which in the operating state extends from the sidewall 28 to the fixed partition 12 and to the upper covering 26, ispassed into the supply air duct 21. As a result of the arresting element37 in the arresting position there is no interchange with ambient air.

In the vicinity of the heat exchanger element 3 there is also anarresting element, but which in FIG. 3 must not be in the arrestingposition and which is not shown so as not to overburden representation.

A locking device for the pivotable partition 10 in the central positionaccording to FIG. 1 and in the two possible blockade positions with thecovering of one of the two heat exchanger elements 3,4 according to FIG.2 is not shown so as not to overburden representation, and also sensorsand air guiding devices in the vicinity of the air intake side and airoutlet side are not shown.

1. Heat A heat exchanger for water-cooled network cabinets having ahousing, which has an air intake side for an exhaust air flow and an airexit side for the cooling air from the heat exchanger and in which thereare two heat exchanger elements arranged at an angle to one another andaccompanied by the formation of a space open on the air intake side,characterized in that comprising for a redundant construction of theheat exchanger the heat exchanger elements have separate cooling waterconnections, that a partition is located in the space between the twoheat exchanger elements and that the partition can be adjusted from aposition for supplying the exhaust air flow to the two heat exchangerelements into a blockade position for the aerodynamic blocking of one ofthe two heat exchanger elements and for supplying the exhaust air flowto the in each case other heat exchanger element.
 2. The heat exchangeraccording to claim 1, wherein the position of the partition forsupplying the exhaust air flow to the two heat exchanger elements is acentral position and that the partition in the blockade position in eachcase covers one of the two heat exchanger elements.
 3. The heatexchanger according to claim 1, wherein the heat exchanger elements areparallelepipedic and positioned in such a way that the air intake-sidespace is in horizontal section V-shaped and an air exit area isvirtually W-shaped.
 4. The heat exchanger according to claim 1, whereinthe partition is positioned vertically and is dimensioned correspondingto the vertical longitudinal side of each heat exchanger elementbounding the space to be covered.
 5. The heat exchanger according toclaim 1, wherein the partition is adjustable about a pivoting axis andthat the pivoting axis is positioned vertically in an area of the spacefacing the air exit side.
 6. The heat exchanger according to claim 1,wherein the partition is adjustable about a pivoting axis, which ispositioned in the vicinity of the mutually adjacent, vertical inneredges of the two heat exchanger elements.
 7. The heat exchangeraccording to claim 1, wherein the heat exchanger elements areconstructed as tubular/finned blocks and are in each case detachablyconnected to the forward and return run of independent lines of a coldwater main or a recooler.
 8. The heat exchanger according to claim 1,wherein each heat exchanger element is located on a separate supportelement and is constructed so as to be extractable together with thegiven support element from the housing of heat exchanger for repair orreplacement purposes.
 9. The heat exchanger according to claim 1,wherein the lower part of the heat exchanger housing is constructed as acondensate/leakage water collecting tank.
 10. The heat exchangeraccording to claim 1, wherein the partition. can be fixed and/or lockedin the central position for normal operation and/or in the two blockadepositions provided in the case of a fault.
 11. The heat exchangeraccording to claim 1, wherein the adjustment of the partition takesplace manually or using a drive and e.g. a gas pressure spring or anelectric motor is provided.
 12. The heat exchanger according to claim 1,wherein in the vicinity of the two heat exchanger elements and theircooling lines are provided sensors for fault detection and for emittingfault and warning signals, particularly flow and leak sensors.
 13. Theheat exchanger according to claim 1, wherein at least in the air exitarea, is provided a fixed partition constructed as an extension of theadjustable partition.
 14. The heat exchanger according to one of thepreceding claims, claim 1, wherein in the air exit area and/or in acabinet area on the air exit side of the heat exchanger are providedadjustable air guiding elements for the distribution over the cabinetwidth of the cooling air flow unilaterally exiting in a partitionblockade position.
 15. The heat exchanger according to claim 1, whereinon the air exit side is provided an air guiding device, which can bedetachably fixed to the heat exchanger housing or to the inside of thecabinet door.
 16. The heat exchanger according to claim 1, wherein it ispositioned at the bottom in a cabinet, particularly a server cabinet,and the cabinet door, which extends to above the heat exchanger, is tobe opened for extracting a heat exchanger element for repair orreplacement purposes.
 17. The heat exchanger according to claim 1,wherein at the bottom it is placed in a cabinet, particularly a servercabinet and a front door of the cabinet extends up to the upper edge ofheat exchanger, that on the air exit side the heat exchanger hasseparate coverings, which are in each case associated with a heatexchanger element and are vertically positioned and that arrestingelements are provided and are in each case associated with a heatexchanger element and in each case can be brought into the arrestingposition after extracting a heat exchanger element in order to preventan interchange of the cooled supply air with ambient air.
 18. The heatexchanger according to claim 1, wherein the heat exchanger elements areconnected via quick couplers to the lines of a cold water main or arecooler.
 19. A method for cooling network cabinets, particularly servercabinets, with the aid of an air-water heat exchanger, comprising thesteps of: in the air-water heat exchanger providing two heat exchangerelements and connecting to separate cooling water connections and thatin normal operation supplying both heat exchanger elements with exhaustair and in the case of a fault one heat exchanger element isaerodynamically blocked and the other heat exchanger element is suppliedwith all the exhaust air.
 20. The method according to claim 19, whereinthe cooling air which in normal operation passes out of both heatexchanger elements and in the case of a fault from only a single elementis supplied to the inner area of the network cabinet via a frontalsupply air duct.
 21. The method according to claim 19, wherein in thecase of a failure of a heat exchanger element or a cooling circuit, thegiven heat exchanger element is aerodynamically blocked and the networkcabinet with the intact heat exchanger element and/or with the supplyair sidedoor opened, is cooled by the ambient air.
 22. The methodaccording to claim 19, wherein there is a flow through the heatexchanger elements from the rear in the direction of the front of thecabinet and if a fault occurs one heat exchanger element is blocked withthe aid of an air intake-side partition.
 23. The method according toclaim 19, wherein the cooling air passing out of the heat exchangerelements is guided separately and distributed with the aid of airguiding elements into a cabinet supply air duct.
 24. The methodaccording to claim 19, wherein the heat exchanger elements are placed onseparate support elements and can be extracted from the heat exchangerhousing and/or the cabinet, without interrupting operation, for repairor disassembly purposes.
 25. The method according to claim 19, whereinthe cooling air flow passing out of a heat exchanger element in the caseof a fault is directed and spread out with the aid of air guidingelements over the entire cabinet width and that the cooling air flowmixed with ambient air or with the aid of coverings on the front and topof the air exit area of each heat exchanger element the exiting coolingair is supplied in unmixed form to the cabinet interior.